Original paper
The use of a new generation self-expanding stent, Vascuflex SEC, for carotid artery stenting

Introduction

In the last decade carotid artery stenting with temporary cerebral protection devices has become increasingly adopted in the treatment of patients with atherosclerotic lesions of brain supplying arteries. A randomized controlled trial, CREST, published in 2010 demonstrated similar direct and long-term results of carotid artery stenting (CAS) and carotid endarterectomy (CEA) [1, 2]. Conditions which determine an optimal result of a carotid artery stenting procedure include operator experience and adequate stent and protection device selection tailored to the patient’s clinical condition, atherosclerotic plaque morphology and the anatomy of the carotid artery [3-5]. Continuous progress and reduction of periprocedural complications are influenced by progressive modernization of the equipment used and most importantly by the construction of new types of protection devices and stents. Self-expanding stents are routinely used for internal carotid artery stenting (ICA) except stenting of the stenosed ostium of the common carotid artery and brachiocephalic trunk where metal stents mounted on a balloon are used. Self-expanding stents used for CAS procedures may be divided according to design into open-cell and closed-cell, each possessing different construction. Differences in the design and characteristics of self-expanding stents influence the strategy of the CAS procedure. Closed-cell or open-cell stents should be selected during the procedure according to atherosclerotic plaque morphology, the presence of neurological symptoms and the anatomy of the treated carotid artery [3-5]. Based on their own experience, the centres performing CAS should be equipped with stents of different design including hybrid stents. Several large registres suggested that the use of only one stent type and one protection device type (usually filter) in all treated patients and lessions can be associates with a high complication rate.

It should be noted that the criteria of an acceptable complication rate (death, stroke, myocardial infarction) for interventional treatment of carotid artery stenosis with cut-off values of 6% in symptomatic patients and 3% in asymptomatic patients are still valid [6]. Therefore each new device dedicated to carotid artery stenting should be introduced into practice in centres with extensive experience in CAS procedures. We present the treatment results in 50 consecutive patients who underwent internal carotid artery stenting with different temporary cerebral protection devices and a new generation self-expanding, open-cell stent – Vascuflex SEC.

Material and methods

Between January and April 2010 a consecutive group of 50 patients underwent carotid artery stenting with different protection devices according to the “Tailored CAS” algorithm [4] with implantation of a new generation self-expanding stent, Vascuflex SEC. Prior to the procedure all patients had ultrasound Doppler of the carotid arteries and angio-CT of the aortic arch and brain supplying arteries. Duplex examination supplied by colour Doppler study initially estimates the degree of artery stenosis and characterizes atherosclerotic plaque morphology. Angio-tomography helps in pre-procedural assessment of the type of aortic arch and in detection of potential anomalies of brain supplying arteries as well as in quantitative assessment of stenosis morphology (from adipose through fibrotic to highly calcified). Both of those non-invasive studies help in initial planning of the carotid artery stenting procedure. Qualification for the procedure included symptomatic patients with > 50% stenosis or asymptomatic patients with  80% stenosis. All patients were qualified for the procedure by an independent neurologist and underwent neurological assessment by the same neurologist directly after CAS, at discharge and at 30 days after the procedure. All patients received dual antiplatelet therapy (aspirin 75 mg/day + clopidogrel 75 mg/day) once daily for at least 3 days before and after the procedure. Postprocedural antiplatelet therapy included clopidogrel for three months and lifelong aspirin.

A selective coronary angiography was performed in all patients before the carotid artery stenting procedure to determine the risk of periprocedural complications. In cases of severe coronary artery disease patients were qualified for percutaneous coronary intervention (PCI) or coronary artery bypass grafting (CABG) at later term. All hypotensive, diuretic and anti-arrhythmic drugs were withheld on the day of the procedure and all patients received 500 ml of isotonic saline before the procedure. In all patients carotid artery stenting was performed with the use of cerebral protection devices. A subgroup of 20 patients was assessed for the feasibility of intraprocedural use of intravascular ultrasound with virtual histology (IVUS-VH) to optimize the selection of neuroprotective device and stent post-dilation. A proximal protection device (MoMa/GNPS system) was used in all symptomatic patients with high risk stenosis (critical, tortuous, long or ulcerated lesion with the presence of thrombus). The type and number of protection devices used in the presented group are shown in table 1.

All patients received a nitinol self-expanding open-cell stent – Vascuflex SEC.

An example of a procedure in a symptomatic, high-risk patient where a proximal cerebral protection device and Vascuflex SEC stent were used is presented in figure 1. During the procedure patients received unfractionated heparin to maintain activated clotting time (ACT) of 250-300 s. All patients, except those with an implanted pacemaker, received 0.5-1.0 mg of atropine before stent implantation. Most patients underwent direct stent implantation. Post-dilation was performed in all patients to maximally optimise the result of the procedure, with residual stenosis not exceeding 30%. All patients underwent pre- and postprocedural intracranial angiography to exclude periprocedural embolic complications. In most patients (after initial femoral artery angiography) the arterial puncture site was closed using a closure device to allow faster patient mobilization after the procedure. An ultrasound examination was performed before discharge and 30 days after CAS to check the implanted stent. A neurological consultation was done to assess any neurological incidents which occurred during 30 days of follow-up.

Results

Between January and April 2010 a group of 50 consecutive patients with critical internal carotid artery stenosis and mean age of 66.4 ±7.9 years (33 men and 17 women) was included in the registry. Demographic data and clinical characteristics of the studied group are presented in table 2. Twenty patients (40%) had a history of neurological incidents during the 6 months preceding CAS. Eight patients (16%) had an occlusion of the contralateral carotid artery. Routinely performed coronary angiography showed the presence of significant coronary artery disease in 33 (66%) patients (tab. 2).

Mean stenosis was 84 ±7.5% (70-99%) before the procedure and 9.1 ±7.7% (0-30%) after the procedure (p < 0.001). Six patients (12%) had pre-procedural stenosis of 95-99%. Intraprocedural assessment of stenosis by means of IVUS-VH was feasible and safe. Proximal protection devices were used in a high percentage of patients (46%). Direct stenting technique was performed in 20 patients (40%). Procedural success of stent implantation was 100% and, in all cases, only one stent was implanted per patient/lesion. In all patients stent implantation was followed by stent post-dilation to obtain residual stenosis not exceeding 30%. An additional stent post-dilation with a 0.5 mm larger balloon was performed in 1 patient (1/20, 5%) after assessment of in-stent minimal lumen area by means of intravascular ultrasound.

There were no cases of major stroke, myocardial infarction or death during CAS, directly after the procedure or throughout the hospitalization period. A minor stroke with complete resolution of symptoms during hospitalization was diagnosed in one patient by the consulting neurologist. There were no signs of intracranial bleeding or acute ischaemic foci in the brain on the CT scan in that patient. A transient ischaemic attack (TIA) occurred in three patients during the procedure. Two of those patients had a contralateral carotid artery occlusion and one had a critical contralateral stenosis. All patients completely recovered before transportation from the cath lab to the ward. There were no cases of death, myocardial infarction or minor stroke between discharge and day 30 of the follow-up. One female patient suffered from major contralateral stroke 5 days after discharge and 7 days after CAS. The stroke occurred in the hemisphere supplied by a chronically occluded carotid artery – contralateral to the stented artery. Ultrasound assessment of the implanted stent showed its good patency and apposition. In-hospital and 30-day complications in symptomatic and asymptomatic patients are presented in table 3. In 40 patients (80%) the femoral artery was closed using the Angioseal 6 or 8 F closure device. Complications at the puncture site in the form of pseudoaneurysm were observed in only one patient and were successfully treated with local thrombin administration.

Statistical analysis was performed by means of non-parametric Wilcoxon test.

Discussion

The growing number of CAS procedures is a result of new guidelines based on the results of recent randomized trials comparing endovascular and surgical treatment indicated high efficacy of percutaneous treatment of atherosclerotic changes in the brain supplying arteries [8, 9]. Several years of experience in carotid artery stenting and the growing significance of proximal devices used for CAS caused a marked reduction of the periprocedural complication rate and a shift from periprocedural towards postprocedural complications [9].

It is estimated that 2/3 of all complications occur after the CAS procedure and are caused by migration of embolic material through the stent cells. Therefore adequate stent apposition to the atherosclerotic plaque and artery wall is crucial and can be best obtained with the use of open-cell stents. A second key element is to avoid embolic material migration through stent cells in the postprocedural period. In this situation closed-cell stents have a marked advantage. The size of self-expandable stent cells varies greatly and ranges from 1.08 mm² for the Carotid Wallstent to 11.48 mm² for the Acculink stent. This characteristic can have an influence on the size of embolic material and therefore clinical consequences caused by migration of atherosclerotic plaque parts to the cerebral circulation. Bosiers et al. [10] demonstrated in their analysis that the use of open-cell stents is related to higher risk of complications in comparison to closed-cell stents. Our studies did not demonstrate differences in direct and long-term results of CAS for both types of stents if cerebral protection devices and, preferably, closed-cell stents are used in symptomatic patients and in patients with high risk lesions [3].

It should be noted that open-cell stents better adapt to tortuous segments of carotid arteries and therefore they have a well-established position as first choice stents in patients with tortuous and calcified carotid arteries treated with the endovascular method [11]. In a 2-year observation period Muller-Hulsbeck et al. found no difference in terms of complications between open- and closed-cell stents implanted in the carotid arteries [12].

In our study using open-cell stents in consecutive patients we registered a very low complication rate of 4%. It should be noted that minor stroke was diagnosed in a patient with partial aphasia which persisted over 24 h following the procedure and resolved without sequelae 5 days after the procedure. A major stroke in the right hemisphere (the third one in 10 years occurring in the presence of ipsilateral carotid artery occlusion) can hardly be related to left internal carotid artery stenting. It should be noted that such good results obtained in a group of 40% of symptomatic patients could have been influenced by the selection of protection devices according to the “Tailored CAS” algorithm. It should also be noted that in 23 patients (46%) a proximal cerebral protection was used (MoMa and GNPS system – tab. 1).

Vascuflex SEC stents have a relatively small area of the cells of 9.3 mm², which also could have influenced the favourable results of the procedure in the analysed group. Nowadays it is hard to perform carotid artery stenting solely with the use of closed-cell stents. The properties of nitinol self-expandable stents are sometimes crucial for a correctly conducted CAS procedure. However, the selection of stent used for carotid artery stenting should be best based on the morphology of the atherosclerotic plaque and on the anatomy of the stenosed artery [3, 4, 12].

Conclusions

Carotid artery stenting with nitinol open-cell Vascuflex SEC stents is a safe procedure. The rate of periprocedural and 30-day complications does not exceed the values accepted by the guidelines. The favourable results obtained using the described stents may have been influenced by the selection of protection devices according to the “tailored CAS” algorithm.

Acknowledgmets

The study was partly supported by the Polish Ministry of Science and Higher Education (grant N N402 184234).

References

 1. Brott TG, Hobson RW, Howard G, et al. Stenting versus endarterectomy for treatment of carotid-artery stenosis. N Engl J Med 2010; 1: 11-23.  

2. Pieniążek P. Nowe spojrzenie na stentowanie tętnic szyjnych w świetle wyników badania CREST. Post Kardiol Interw 2010; 3: 122-125.  

3. Pieniążek P, Musiałek P, Kabłak-Ziembicka A, et al. Carotid artery stenting with patent and lesion tailored selection of the neuroprotection system and stent type: early and 5-year results from a prospective academic registry of 535 consecutive procedures (TARGET-CAS). J Endovasc Therapy 2008; 3: 249-262.  

4. Cremonesi A, Gieowarsing S, Spagnolo B, et al. Safety, efficacy and long-term durability of endovascular therapy for carotid artery disease: the tailored-carotid artery stenting. Experience of a single high volume center (tailored – CASE Registry). Eurointervention 2009; 5: 589-598.  

5. Bosiers M, Deloose K, Verbist J, et al. What practical Factor guide the choice of stent and protection device during carotid angioplasty. Eur J Vasc Endovasc Surg 2008; 35: 637-643.  

6. Goldstein LB, Bushnell CD, Adams RJ, et al. Guidelines for primary prevention of stroke: a guideline for healthcare professionals from the American Heart Association/American Stroke Association. Stroke 2011; 42: 517-584.  

7. Witkowski A. Angioplastyka tętnic szyjnych – przegląd badań, wyniki, współczesne wskazania do zabiegu. Post Kardiol Interw 2007; 3: 15-18.  

8. Brott TG, Helperin JL, Abbara S, et al. ASA/ACCF/AHA/AANN/ACR/ASNR/CNS/SAIP/SCAI/ISIR/SNTS/SVM/SVS Guidelines on the Management of the Patients with Extracranial Carotid and Vertebral Artery Disease. J Am Coll Cardiol 2011; 57: e16-94.  

9. Cremonesi A, Setacci C, Maneti R, et al. Carotid angioplasty and stenting; lesion related treatment strategy. Eurointervention 2005; 1: 289-295.

10. Bosiers M, de Donato G, Deloose K, et al. Does free cell area influence the outcome in carotid artery stenting? Eur J Endovasc Surg 2007; 33: 135-141.

11. Schillinger M, Minar E. Matching carotid anatomy with carotid stents. J Cardiovasc Surg 2008; 49: 723-727.

12. Muller-Hulsbeck S, Preus H, Elhoft H. CAS: which stent for which lesion. J Cardiovasc Surg 2009; 6: 767-772.